Effects of age on lipogenesis and lipolysis in lean and obese swine.

The effects of age on lipogenic and lipolytic activities in several breeds of swine were investigated. Females from a contemporary line and genetically selected populations of lean and obese pigs were utilized. Subcutaneous adipose tissue samples were taken from the shoulder area of nonfasted animals at 28-day intervals from 3 to 6 months of age for determination of in vitro lipogenic, lipolytic and acetyl CoA carboxylase activities. There were no significant differences between the breeds in the in vitro lipogenic rates measured in tissue slices with 14 C-glucose as substrate, except at 6 months of age, when the rate was higher in the obese than in the lean animal. However, the trend each months was obese greater than contemporary greater than lean. Lipogenic activity was greatest in all breeds at 4 months of age. Acetyl CoA carboxylase activity closely paralleled the lipogenic activity. The in vitro unstimulated lipolytic rate measured in tissue slices by the release of fatty acids to the incubation medium was similar for all breeds and decreases with age. Lipogenesis appears to be more important than unstimulated lipolysis in regulating backfat thickness in the breeds of swine examined.